Apple has one big reason to move to a homegrown GPU: It wants full control over the hardware and software in its devices.The device maker is apparently developing its own GPU from scratch after dumping Imagination Technologies' PowerVR architecture, which is being used in the iPhone 7. The smartphone runs on the PowerVR A10 Fusion chip.It's not certain when Apple's homegrown GPU will appear in devices, and the company didn't respond to request for comment.

Quotes

We believe the iPhone 7, to avoid overheating, throttles back from its top GPU speed after a minute or less, preventing it from achieving a high score for all users.

Apple has not presented any evidence to substantiate its assertion that it will no longer require Imagination's technology, without violating Imagination's patents, intellectual property, and confidential information. This evidence has been requested by Imagination but Apple has declined to provide it.